In a small mixing bowl, combine the peppercorns, thyme, bay leaves, cloves, garlic, and whole juniper berries. In a saucepan, over medium heat, combine the water, brown sugar and salt. Bring to a boil and stir to dissolve the sugar and salt. Remove from the heat and add dry spice mixture and steep for 1 hour. Place the chicken in a plastic bag and pour the seasoned brine to cover the completely. Refrigerate overnight, mixing the contents a couple of times. Remove the chicken from the brine and rinse thoroughly with cool water. Pat dry with a towel.

For safety's sake, make sure your brine is at least room temp or colder when you put the chicken in it and then make sure it goes right into the fridge.

Cold packs wrapped in ziplock bags are good for chilling brine.

Alton Brown subs ice cubes for the water to ensure a cold brine.

And you might find that overnight is too long to brine chicken breasts. I only soak mine for 1-3 hours. A whole turkey goes overnight. Pork can brine a lot longer.

Very good points as usual from Jennyema!
For chicken breasts I never go more than two hours in a brine. I would go 3 at max, but I find two works well for me. I once went longer (I don't remember exactly how much longer tho) and the texture was horrible. It felt almost like I was eating raw chicken even though it was cooked through. A whole chicken can brine for longer, but I probably would do 5 or 6 hours. Overnight would be too long for me personally, but try it different ways and find what works best for you.

[QUOTE=jennyema]...Cold packs wrapped in ziplock bags are good for chilling brine.

Alton Brown subs ice cubes for the water to ensure a cold brine...QUOTE]

I make the brine with half the water I plan to use (and all of the other ingredients) and heat it to disolve the sugar and salt and to infuse the flavors of herbs and spices. Then I cool the pan in cold water in the sink and add the second half of the water in the form of ice water and ice cubes.

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"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan